Biomimic design stabilizing fin or keel for surface planing or submerged watercraft

ABSTRACT

A stabilizing fin or keel utilizing biomimic design features for use on surface planing or submerged watercraft to provide increased dimensional stability, control and efficiency.

FIELD OF INVENTION

The invention as presented relates to surface planing or submersiblewatercraft such as surfboards, kiteboards, sailboats, submersible craft,etc. and more specifically to fins or keels employed for dimensionalstability and control of watercraft while in motion through water eitheron water surface or submerged.

BACKGROUND OF INVENTION

This invention relates to surface planing or submerged watercraft suchas surfboards, kiteboards, sailboats, submersible craft, etc. andspecifically to fins or keels of which the primary function of fins orkeels attached to a watercraft surface that contacts water is to providedimensional stability and control of watercraft while moving orpropelled through water either on water surface or submerged. Thepresent invention improves on existing designs by providing an increasedarea of lateral flex (leading edge to trailing edge) that is notfeatured in existing designs. The number, shape, size, and location offins or keels is dependent on the desired function and performance ofsaid watercraft. For example, as a watercraft moves through water in aforward direction the water flow and water pressure or hydrodynamicpressure are equal on either side of a fin or keel. As direction ofwatercraft changes (i.e. Turning or tacking) water pressure orhydrodynamic pressure increases on the turns inner radius side of fin orkeel and decreases on the turns outer radius side of fin or keelsurface. When the water pressure or hydrodynamic pressure becomes toogreat on the inner radius side of fin or keel and too deficient on theouter radius side of fin or keel the low pressure side produces a lowpressure core in the laminar flow boundary resulting in cavitating flow.At the point when a fin or keel produces cavitating flow the fin or keelloses the ability to provide dimensional stability resulting in the lossof control of watercraft by operator. The invention as presentedprovides several novel improvements over current or traditional fin orkeel designs.

Borrowing from the natural design of the fins of fish and cetaceans alsoknown as biomimicry, the invention as presented increases efficiency andimproves performance of fins or keels by reducing cavitating flow duringdirectional changes by allowing the rear portion of fin or keel to reactby flexing laterally in proportion to increasing water pressure on finor keel surface experienced while turning or tacking of said watercraft.There are several patents directed toward fins or keels featuring alateral flex component employed for dimensional stability and control ofsurface planing or submerged watercraft. These devices are limited intheir functionality by either the degree of lateral flex or thedistribution of lateral flex area.

Lewis, U.S. Pat. No. 5,480,331 discloses a flexible fin for surfboardscomprised of a fiberglass core sandwiched between two closed cellpolyurethane foam surface layers.

Skedeleski/Arakawa, U.S. Pat. No. 5,306.188 discloses a surfboard finconsisting of a rigid body element with a soft flexible materialcovering the leading and trailing edges of fin. The soft flexibleleading edge and the soft flexible trailing edge reduces injury fromimpact of fin to surfer and provides a rudder action by flexing duringturns.

Additional advantages are an increase in watercraft speed by reducingturbulence of laminar flow exiting fins or keels and reduction of fin orkeel weight by reduction of fin or keel volume. Additional advantages,objects, and novel features will become apparent when reviewing thedetailed description and claims in conjunction with the detaileddrawings.

BRIEF SUMMARY OF INVENTION

The present invention consists of a rigid convex leading edge foilelement located at the forward leading edge of fin or keel curving fromthe leading edge end point of fin or keel base to the fin or keel tipand the tapering trailing edge of rigid convex foiled fin or keelelement curving from fin or keel tip to fin or keel base terminating attapered trailing edge end point of fin or keel base, comprising 50-60%of total fin or keel area. A thin flexible element located at the reartapered trailing edge area of rigid convex leading edge elementextending to trailing edge of fin or keel and curving from fin or keeltip to fin or keel base terminating at the tapered trailing edge endpoint of fin or keel base comprising 40-50% of total area of fin or keelarea.

BRIEF DESCRIPTION

A stabilizing fin or keel may vary in size and shape but several designfeatures are fundamental consisting of a vertical plane, a radiusleading edge curving from the frontal end point of fin or keel base tothe fin or keel tip, a tapered trailing edge curving from the rear endpoint of fin or keel base to the fin or keel tip, a fin or keel tipwhere leading and trailing edges intersect, and a fin or keel base wherefin or keel is attached perpendicular to watercraft surface contactingwater by either mechanical means or permanently bonded to the surface ofa watercraft. The present invention is a fin or keel that extendsperpendicular to a surface of a watercraft contacting water comprisingof a rigid leading edge convex foiled element (FIG. 1 #14) curving fromfin or keel base frontal end point to fin or keel tip, a rigid convexfoil trailing edge curving from fin or keel tip terminating at reartrailing edge end point of fin or keel base comprising 50-60% of totalfin or keel area. A thin flexible trailing edge element (FIG. 1 #18)extending from the trailing edge of rigid convex leading edge element tothe trailing edge of fin or keel curving from fin or keel tip to fin orkeel base terminating at trailing edge end point of fin or keel basecomprising of 40-50% of total fin or keel area. A flat base of fin orkeel extending from leading edge end point to trailing edge end pointproviding a means of attachment to watercraft surface by mechanicalmeans or permanently bonded.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to fins and keels that are utilized fordimensional stability and control of watercraft in motion planing onwater surface or submerged.

The present invention improves on current fin or keel designs byutilizing a thin flexible element positioned in the rear trailing edgearea of fin or keel and providing leading edge to trailing edge lateralflex to fin or keel providing increased stability, control andefficiency of a surface planing or submerged watercraft in motion byreducing a fin or keels development of a cavitating flow in the laminarflow boundary, reducing turbulence in laminar flow exiting a fin or keeland reducing fin or keel weight. Cavitating flow occurs when waterpressure or hydrodynamic pressure increases on the inner radius side ofa fin or keel and decreases on the outer radius side of fin or keelduring directional changes (i.e. turns or tacks). When the waterpressure or hydrodynamic pressure becomes too great on the inner radiusside of fin or keel and too deficient on the outer radius side of fin orkeel a low pressure core develops in the laminar flow boundary resultingin cavitating flow and the loss of fin or keels ability to providedimensional stability. The present invention reduces cavitating flow byproviding an increased flexible trailing edge area which allows lateralflexibility of fin or keel from leading edge to trailing edge whereascurrent designs provide a minimal amount of lateral flex. Utilizingdesign elements occurring in nature also known as biomimicry (seereference-Janine Benyus/Biomimicry:Innovation inspired by nature-1997)and more specifically relating to the fins of fish and cetaceans, thepresent invention provides a reduction of a fin or keels development ofcavitating flow during directional changes or turns by utilizing anincreased flexible element area which flexes laterally in response toincreasing water pressure or hydrodynamic pressure on the inner radiusside of a fin or keel during a directional change providing an increasein efficiency and control of a watercraft in motion by reducingcavitational flow. The present invention consists of a rigid convexfoiled leading edge element comprising of the frontal edge of rigidconvex foil element curving from fin or keel base frontal end point tofin or keel tip and trailing edge of rigid convex foil element curvingfrom fin or keel tip to trailing edge rear end point of fin or keel basecomprising 50-60% of total fin or keel area. A thin flexible trailingedge element extending from trailing edge of rigid convex foil elementto fin or keel trailing edge and curving from fin or keel tip to fin orkeel base terminating at trailing edge end point of fin or keel basecomprising 40-50% of total fin area.

In order for the leading edge element to provide the desired rigidity avery stiff composite such as carbon fiber or similar material isutilized which is laminated with epoxy or a similar resin. In order forthe flexible trailing edge element to provide the desired flexibility ahigh shear strength composite fabric such as Innegra-s or Kevlar orsimilar material is utilized which is laminated using a flexible epoxyor similar resin. Rigid convex foiled leading edge element and thinflexible trailing edge element are integrally bonded. In one embodimentof the present invention a fin or keel attached to the bottom surfacepositioned in the rear area of a surfboard providing dimensionalstability to the rider. A rider standing on the top surface of asurfboard riding a wave will initiate a turn by shifting their weight orleaning in the the direction they desire the surfboard to turn. During aturn water pressure increases on the inner radius side of fin and waterpressure decreases on the outer radius side of fin. During extreme turnswater pressure greatly increases on the fins inner radius side andgreatly decreases on the fins outer radius side of fin. When waterpressure decreases to a critical point on the outer radius side of fin alow pressure core develops in the laminar flow boundry producingcavitational flow and loss of dimensional stability of fin or keelresulting in loss of control of surfboard by the rider. In thisembodiment of the present invention the increase in trailing edgelateral flex area releases water pressure on inner radius side of fin orkeel reducing the development of a low pressure core and cavitationalflow. The present invention provides a reduction of disproportionatewater pressure on fin surfaces during directional changes (turns, tacks)providing dimensional stability to watercraft in motion. Additionaladvantages, objects and novel features will become apparent whenreviewing the detailed description of drawings and claims in conjunctionwith the detailed description.

The present invention provides several improvements on current designs(reference-Skedeleski-U.S. Pat. No. 5,306,188, Lewis-U.S. Pat. No.5,480,331) by incorporating a thin flexible trailing edge elementallowing for greater lateral flex of said fin or keel. In one embodimentof the present invention a fin attached to a surfboard perpendicular tothe bottom surface of a surfboard in the rear area of a surfboardproviding dimensional stability to the rider. A rider standing on thetop surface of a surfboard riding a wave will initiate a turn byshifting their weight or leaning in the direction they desire thesurfboard to turn. During a turn water pressure or hydrodynamic pressureincreases on turns inner radius side of fin and decreases on the turnsouter radius side of fin. During extreme turns water pressure orhydrodynamic pressure greatly increases on the turns inner radius sideof fin and significantly decreases on the outer radius side of fin. Whenthe water pressure or hydrodynamic pressure on the outer radius side offin decreases to a critical point the fin develops a low pressure corein the laminar flow boundary producing cavitating flow causing loss ofdimensional stability of fin or keel resulting in rider losing controlof surfboard. In this embodiment of the present invention the increasedarea of the flexible trailing edge element provides lateral flexresulting in the release of water pressure or hydrodynamic pressure onthe fin or keels inner radius side and reducing the decrease in waterpressure or hydrodynamic pressure on the outer radius side of fin orkeel therefore reducing the development of a low pressure core andsubsequent cavitating flow in the laminar flow boundary. The presentinvention provides a reduction in disproportionate water pressure orhydrodynamic pressure on fin or keel surfaces during directional changes(turns, tacks) and provides greater dimensional stability of awatercraft in motion on water surface or submerged. Additionaladvantages, objects, and novel features will become apparent whenreviewing the detailed description and claims in conjunction withdrawings and description of drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 Is a side perspective view of stabilizing fin of presentinvention

FIG. 2 Is a side perspective view of stabilizing fin illustratingsurface contours of the present invention

FIG. 3 Is a front perspective view of stabilizing fin of the presentinvention FIG. 4 Is a rear perspective view of stabilizing fin of thepresent invention showing rigid element #14 and flexible element #18

FIG. 5 Is a cross sectional perspective view of stabilizing fin of thepresent invention taken along lines 11-11 showing the rigid element ofthe stabilizing fin at fin base

FIG. 6 Is a cross sectional perspective view of stabilizing fin of thepresent invention taken along lines 10-10 showing rigid element #14 andflexible element #18

FIG. 7 Is a cross sectional view of a surfboard taken along lines 22-22of FIG. 7 showing the location of the stabilizing fins of the presentinvention's attachment to the bottom surface of a surfboard

FIG. 8 Is a side perspective view of surfboard showing location ofstabilizing fins of the present invention attached to bottom surface ofsurfboard at rear area of surfboard

FIG. 9 Is a bottom perspective view of surfboard showing center line #25and stabilizing fins location in rear area of surfboard illustratingflexible component of stabilizing fins of the present invention bydotted lines

REFERENCES CITED

5,306,188 Skedeleski Apr. 26, 1994 5,480,331 Lewis Jan. 2, 1996

Reference for term biomimicry Janine Benyus—Biomimicry: InnovationInspired by Nature—1997

DETAILED DESCRIPTION OF DRAWINGS

10. cross sectional view taken along lines 10-10 of FIG. 1

11. cross sectional view taken along lines 11-11 of FIG. 1

12. fin (center)

13. fin tip

14. rigid convex foil element

15. rigid convex foil element fin base

16. leading edge rigid convex foil element—FIG. 1

17. trailing edge rigid convex foil element—FIG. 1

18. thin flexible element—FIG. 1

19. trailing edge thin flexible element—FIG. 1

20. leading edge rigid convex foil element fin base—FIG. 1

21. trailing edge rigid convex foil element—FIG. 1

22. cross section of rear area of surfboard taken along lines 22-22 FIG.1

23. surfboard top surface—FIG. 7

24. surfboard bottom surface—FIG. 7

25. center line of surfboard—FIG. 9

26. rear or tail section of surfboard—FIG. 9

27. left side fin and right side fin

I claim:
 1. A stabilizing fin or keel utilizing biomimic design forsurface planing or submerged watercraft comprising: a. A vertical rigidconvex foil leading edge element comprising of a leading edge curvingfrom frontal leading edge end point of fin or keel base to fin tip, anda trailing edge of rigid convex foil element curving from fin tip torear end point of fin or keel base comprising 50-60% of total fin area.b. A vertical trailing edge element comprising of a thin flexiblematerial extending from trailing edge of rigid convex foil element tofin or keel trailing edge and curving from fin or keel tip to rear endpoint of fin or keel base comprising 40-50% of total fin or keel area.c. A leading edge curving from frontal end point of fin base to fin tip.d. A trailing edge curving from rear end point of fin base to fin tipwith both leading edge and trailing edge intersecting at fin tip. e. Aflat base extending from leading edge end point to trailing edge endpoint providing an area for attachment to watercraft surface by eithermechanical means or permanently bonded. Wherein during use flexibletrailing edge element reacts to increasing water pressure orhydrodynamic pressure on the fin or keels inner radius surface during adirectional change (turn, tack) by flexing laterally reducingdisproportionate water pressure or hydrodynamic pressure on fin or keelsurfaces decreasing the development of a low pressure core andsubsequent cavitational flow in the laminar flow boundary of outerradius side of a fin or keel improving dimensional stability and controlof watercraft.
 2. The stabilizing fin or keel of claim 1 whereas theleading edge rigid convex foil element and the thin flexible trailingedge element are integrally connected.
 3. A stabilizing fin or keelutilizing biomimic design for surface planing or submerged watercraftcomprising: a rigid convex foil leading edge element curving fromfrontal end point of fin or keel base to fin or keel tip and trailingedge of rigid convex leading edge element curving from fin or keel tipterminating at trailing edge end point of fin or keel base. a thinflexible trailing edge element 2 millimeters in thickness comprised ofone layer of a high shear strength composite fabric (i.e. Kevlar orsimilar material) sandwiched between two layers of woven fiberglasscloth or similar material laminated using a flexible epoxy or similarresin extending from trailing edge of rigid convex foil leading edgeelement to trailing edge of fin or keel curving from fin or keel tip totrailing edge end point of fin or keel base. whereas rigid convexleading edge element and thin flexible trailing edge element areintegrally connected. a flat base extending from leading edge end pointto trailing edge end point providing an area for attachment to awatercraft surface contacting water by mechanical means or permanentlybonded. wherein during use the thin flexible element reduces turbulencein laminar flow exiting fin or keel by decreasing water displacement offin or keel.
 4. A stabilizing fin or keel utilizing biomimic design forsurface planing or submerged watercraft comprising: a rigid convex foilleading edge element curving from frontal end point of fin or keel baseto fin or keel tip and trailing edge of rigid convex leading edgecurving from fin or keel tip to trailing edge end point of fin or keel.whereas rigid convex foil leading edge element and thin flexibletrailing edge element are integrally connected. a flat base extendingfrom leading edge end point to trailing edge end point providing an areafor attachment to a watercraft surface contacting water by mechanicalmeans or permanently bonded. wherein the reduction of fin or keel volumeprovides a reduction in fin or keel weight enhancing performance ofsurface planing or submerged watercraft.